Method and an Apparatus for Processing an Audio Signal

1. A method of decoding an audio signal, the method comprising: extracting spectral data and loss signal compensation information from an audio signal bitstream, wherein the loss signal compensation information indicates whether a current frame performs loss signal compensation using a loss signal compensation parameter, and wherein the loss signal compensation information is extracted from a frequency domain; when the loss signal compensation information indicates that the current frame performs the loss signal compensation, extracting the loss signal compensation parameter from the audio signal bitstream, wherein the loss signal compensation parameter includes a scale factor reference value and loss signal level information; determining whether a current band included in the current frame is a band quantized to zero by detecting a loss signal based on the spectral data; generating a compensation level information using the loss signal level information, wherein the compensation level information indicates an absolute value for replacing the current band when the current band is determined to be the band quantized to zero; when the current band is determined to be the band quantized to zero, generating first compensation data corresponding to the current band using a random signal and the compensation level information, and generating a modified scale factor corresponding to the current band by adding a scale factor to the scale factor reference value, wherein the scale factor is information to scale the first compensation data, and wherein the scale factor reference value is information for modifying the scale factor for the current frame; generating second compensation data by applying the modified scale factor to the first compensation data; generating a loss reconstruction signal using the second compensation data; determining whether the loss reconstruction signal is an audio characteristic or a speech characteristic based on whether the loss reconstruction signal is a harmonic signal having high redundancy on a time axis; when the loss reconstruction signal is the audio characteristic, decoding the loss reconstruction signal based on an audio coding scheme; and when the loss reconstruction signal is the speech characteristic, decoding the loss reconstruction signal based on a speech coding scheme, wherein the current band is a scale factor band.

2. The method of claim 1 , wherein the first compensation data has a level that is less than or equal to a specific value corresponding to the compensation level information.

3. The method of claim 1 , wherein the second compensation data corresponds to a spectral coefficient.

4. An apparatus for decoding an audio signal, the apparatus comprising: a demultiplexer configured to extract spectral data and loss signal compensation information from an audio signal bitstream, wherein the loss signal compensation information indicates whether a current frame performs loss signal compensation using a loss signal compensation parameter, wherein the loss signal compensation information is extracted from a frequency domain, wherein, when the loss signal compensation information indicates that the current frame performs the loss signal compensation, the demultiplexer is further configured to extract the loss signal compensation parameter from the audio signal bitstream, and wherein the loss signal compensation parameter includes a scale factor reference value and loss signal level information; a loss signal detecting unit configured to: determine whether a current band included in the current frame is a band quantized to zero by detecting a loss signal based on the spectral data, and generate a compensation level information using the loss signal level information, wherein the compensation level information indicates an absolute value for replacing the current band when the current band is determined by the loss signal detecting unit to be the band quantized to zero; a compensation data generating unit configured to generate first compensation data corresponding to the current band using a random signal and the compensation level information when the current band is determined by the loss signal detecting unit to be the band quantized to zero; a re-scaling unit configured to generate a modified scale factor corresponding to the current band by adding a scale factor to the scale factor reference value when the current band is determined by the loss signal detecting unit to be the band quantized to zero, wherein the scale factor is information to scale the first compensation data, wherein the scale factor reference value is information for modifying the scale factor for the current frame, and wherein the re-scaling unit is further configured to generate second compensation data by applying the modified scale factor to the first compensation data; and a loss signal compensator configured to generate a loss reconstruction signal using the second compensation data; and an audio decoder configured to: determine whether the loss reconstruction signal is an audio characteristic or a speech characteristic based on whether the loss reconstruction signal is a harmonic signal having high redundancy on a time axis, when the loss reconstruction signal is the audio characteristic, decode the loss reconstruction signal based on an audio coding scheme, and when the loss reconstruction signal is the speech characteristic, decode the loss reconstruction signal based on a speech coding scheme, wherein the current band is a scale factor band.

5. The apparatus of claim 4 , wherein the first compensation data has a level that is less than or equal to a specific value corresponding to the compensation level information.

6. The apparatus of claim 4 , wherein the second compensation data corresponds to a spectral coefficient.

7. The method of claim 1 , further comprising: generating the scale factor based on a scale factor difference value if the scale factor does not correspond to a band having all spectral data samples quantized to zero.

8. The apparatus of claim 4 , wherein the re-scaling unit generates the scale factor based on a scale factor difference value if the scale factor does not correspond to a band having all spectral data samples quantized to zero.

9. The method of claim 1 , further comprising: generating a spectral data of a high frequency band using the second compensation data, wherein a frequency of the high frequency band is higher than a frequency of the current frame.

10. The apparatus of claim 4 , further comprising: a band extension decoder configured to generate a spectral data of a high frequency band using the second compensation data, wherein a frequency of the high frequency band is higher than a frequency of the current frame.